Direct smelting process

ABSTRACT

A molten bath-based direct smelting process comprises controlling the process conditions in a direct smelting yessel so that molten slag in a molten bath of metal and slag in the vessel has a viscosity in a range of 0.5-5 poise when the slag temperature is in a range of 1400-1550° C. in the molten bath in the vessel.

The present invention relates to a molten bath-based direct smeltingprocess for producing molten metal from a metalliferous feed materialthat contains iron oxides and titanium oxides in a direct smeltingvessel.

The metalliferous feed material may be any material that contains ironoxides and titanium oxides. One example of a suitable feed material istitanium magnetite. This is also known as titanomagnetite or “ironsands”. Another example is ilmenite. Suitable sources of titaniummagnetite are found in SW China, and NZ. Suitable sources of ilmeniteare found in Western Australia and Madagascar. The present invention isnot confined to titanium magnetite and ilmenite and is not confined totitanium magnetite and ilmenite from these sources.

The metalliferous feed material may also be any material that containsiron oxides and titanium oxides and other metal oxides such as vanadiumoxides. One example of a suitable feed material is titanium-vanadiummagnetite, such as found in SW China and NZ or as a residue from a TiO₂pigment feed process (such as the Becher process).

A known molten bath-based direct smelting process is generally referredto as the HIsmelt process, is described in a considerable number ofpatents and patent applications in the name of the applicant.

The HIsmelt process is associated particularly with producing molteniron from iron ore.

In the context of producing molten iron, the HIsmelt process includesthe steps of:

(a) forming a bath of molten iron and slag in a direct smelting vessel;

(b) injecting into the bath: (i) iron ore, typically in the form offines; and (ii) a solid carbonaceous material, typically coal, whichacts as a reductant of the iron ore feed material and a source ofenergy; and

(c) smelting iron ore to iron in the bath.

The term “smelting” is herein understood to mean thermal processingwherein chemical reactions that reduce metal oxides take place toproduce molten metal.

In the HIsmelt process solid feed materials in the form of metalliferousmaterial and solid carbonaceous material are injected with a carrier gasinto the molten bath through a number of lances which are inclined tothe vertical so as to extend downwardly and inwardly through the sidewall of the direct smelting vessel and into a lower region of the vesselso as to deliver at least part of the solid feed materials into themetal layer in the bottom of the vessel. The solid feed materials andthe carrier gas penetrate the molten bath and cause molten metal and/orslag to be projected into a space above the surface of the bath and forma transition zone. A blast of oxygen-containing gas, typicallyoxygen-enriched air or pure oxygen, is injected into an upper region ofthe vessel through a downwardly extending lance to cause post-combustionof reaction gases released from the molten bath in the upper region ofthe vessel. In the transition zone there is a favourable mass ofascending and thereafter descending droplets or splashes or streams ofmolten metal and/or slag which provide an effective medium to transferto the bath the thermal energy generated by post-combusting reactiongases above the bath.

Typically, in the case of producing molten iron, when oxygen-enrichedair is used, it is fed at a temperature of the order of 1200° C. and isgenerated in hot blast stoves. If technically pure cold oxygen is used,it is typically fed at or close to ambient temperature.

Off-gases resulting from the post-combustion of reaction gases in thedirect smelting vessel are taken away from the upper region of thevessel through an off-gas duct.

The direct smelting vessel includes refractory-lined sections in thelower hearth and water cooled panels in the side wall and the roof ofthe vessel, and water is circulated continuously through the panels in acontinuous circuit.

The HIsmelt process enables large quantities of molten iron, typicallyat least 0.5 Mt/a, to be produced by direct smelting in a single compactvessel.

However, the view of the applicant up to this point in time has beenthat the HIsmelt process is not suitable for smelting metalliferous feedmaterial that contains iron oxides and titanium oxides such astitanomagnetite and ilmenite and optionally also contains other metaloxides such as vanadium oxides. The applicant has now carried outresearch and development work on the HIsmelt process, particularly workinvestigating the characteristics of the slag in the process, thatindicates that appropriate control of process conditions makes itpossible to smelt metalliferous feed material that contains iron oxidesand titanium oxides and optionally vanadium oxides in the HIsmeltprocess. This finding also applies to other molten bath-based processesthat have similar characteristics to or incorporate the HIsmelt process.

The above discussion is not intended to be an admission of the commongeneral knowledge in Australia and elsewhere.

The present invention provides a molten bath-based direct smeltingprocess that comprises controlling the process conditions in a directsmelting vessel so that molten slag in a molten bath of metal and slagin the vessel has a viscosity in a range of 0.5-5 poise when the slagtemperature is in a range of 1400-1550° C. in the molten bath in thevessel.

The present invention provides a direct smelting process that comprisessupplying (a) a metalliferous feed material that contains iron oxidesand at least 3 wt. % titanium oxides (b) a solid carbonaceous feedmaterial, and (c) an oxygen-containing gas into a direct smelting vesselcontaining a molten bath of iron and slag and direct smelting themetalliferous feed material in the vessel and producing process outputsof molten iron, molten slag containing titanium oxides, and an off-gas,and the process being characterised by controlling the processconditions, as described herein, so that the molten slag has a viscosityin a range of 0.5-5 poise when the slag temperature is in a range of1400-1550° C. in the molten bath in the direct smelting vessel.

The term “molten slag” is understood herein to mean slag that iscompletely liquid.

The term “molten slag” is also understood herein to mean slag thatcomprises a slurry of a solid material and a liquid phase.

The solid material in the molten slag may be a solid oxide phase at theslag temperature in the process, whereby the slag is a slurry of a solidoxide phase in a liquid slag phase.

The term “process conditions” is intended herein to have a wide meaningand to extend, by way of example, to (a) operating conditions within thedirect smelting vessel, such as temperature and pressure and injectionrates of the solid feed materials and the oxygen-containing gas into thevessel, (b) the composition of the molten bath, particularly the slagcomposition, and (c) the characteristics of the molten bath. Thecomposition of the molten bath may include the selection of theconstituents of the slag so that the slag is a molten slag, as describedherein, in the temperature range of 1400-1550° C. of the molten bath. Asindicated in the definition of “molten slag” set out above, the moltenslag may include a solid oxide phase and a liquid slag phase at theoperating temperature range of the process. The characteristics of themolten slag include, by way of example, the viscosity and/or the oxygenpotential of the molten slag mentioned above. The characteristics alsoinclude by way of example, the basicity of the molten slag and theturbulence of the slag. These characteristics are a function ofoperating conditions and slag composition.

The present invention is based on a realisation of the applicant as aconsequence of the above-mentioned research and development work that:

-   -   (a) there are operating windows for direct smelting        metalliferous feed materials that contain iron oxides, titanium        oxides and optionally vanadium oxides in the HIsmelt process and        other molten bath-based processes that have similar        characteristics to or incorporate the HIsmelt process and;    -   (b) molten bath-based processes operating within these windows        provide an opportunity to smelt these titaniferous materials to        produce molten iron more effectively than is the case in blast        furnaces that are currently being used to smelt        titanomagnetites, including titanomagnetites that contain        vanadium oxides.

In particular, the applicant has realised that the present inventionprovides an opportunity to produce two valuable products from moltenbath-based smelting processes of the HIsmelt type process, namely (a) amolten iron product which may contain vanadium metal and (b) a slagproduct that has high concentrations of titanium oxides in the form ofTiO₂, such as at least 50%, that can be used as a feed material for thesulphate process for producing pigment-grade titania. In particular, theapplicant has realised that there is an opportunity with moltenbath-based processes to control the cooling rate of the molten slagdischarged from the process to preferentially form microstructures thatare amenable to processing in the sulphate process.

The process may comprise controlling the process conditions bycontrolling the slag composition and the temperature of the molten bathto be below, typically slightly below, the liquidus temperature of theslag so that a solid oxide phase precipitates from a liquid phase of themolten slag, thereby controlling the viscosity of the slag.

The terms “viscosity” and “liquidus temperature” as used herein areunderstood to mean the viscosity and liquidus temperature as calculatedby FactSage software (for liquidus temperature, FactSage 6.1 or laterand for viscosity “FactSage Viscosity 6.0 or later”). Given thepotential for non-standard results arising from different measuring andcalculation techniques, rationalisation via FactSage calculation isdefined to be implicit in the meaning of these terms. Such calculations,when executed, are to be fully consistent with guidelines for using theFactSage software and, if necessary, are to be reviewed and authorisedby the owners of the FactSage software. In particular, calculationswhich (deliberately or otherwise) omit certain possible chemical speciescombinations will not be considered consistent with “viscosity” and“liquidus temperature” as used herein.

The process may comprise controlling the process conditions so that thesolid material in the molten slag is at least 5% of the molten slag.

The solid material in the molten slag may be at least 10% of the moltenslag.

The solid material in the molten slag may be less than 30% of the moltenslag.

The solid material in the molten slag may comprise 15-25% of the moltenslag.

The metalliferous feed material may be any material that contains ironoxides and titanium oxides. Examples of suitable feed materials aretitanium magnetite, titanomagnetite and ilmenite.

In situations where the metalliferous feed material comprisestitanomagetite only, the titanium oxides may be less than 40 wt. % ofthe metalliferous feed material.

In situations where the metalliferous feed material comprisestitanomagetite only, the titanium oxides may be less than 30 wt. % ofthe metalliferous feed material.

In situations where the metalliferous feed material comprisestitanomagetite and ilmenite, the titanium oxides may be less than 50 wt.% of the metalliferous feed material.

The metalliferous feed material may also be any material that containsiron oxides and titanium oxides and other metal oxides such as vanadiumoxides. One example of a suitable feed material is titanium-vanadiummagnetite.

In situations where the metalliferous material contains vanadium oxides,the process includes producing process outputs of molten iron andvanadium, molten slag containing titanium oxides and vanadium oxides,and an off-gas.

Depending on the process conditions, the partition of vanadium betweenthe metal and slag outputs of the process may be at least 50%, typicallyat least 65%, more typically at least 80%, to the metal output.

In general terms, and not only in situations where the metalliferousmaterial contains vanadium oxides, the process may comprise controllingthe process conditions by controlling the ratio of the concentrations ofiron in the slag to carbon in the metal to be less than 2:1, typicallyless than 1.5:1, more typically 1:1 to 1.3:1.

The process may comprise controlling the process conditions so that themolten slag has a high oxygen potential.

The term “high” in the context of “oxygen potential” is understoodherein to mean high in relation to blast furnace slag.

The process may comprise controlling the process conditions so that theoxygen potential of the molten slag is sufficiently high to minimisereduction of titanium oxides in the slag from a +4 valence state to alower valence state. Lower valence states reduce slag viscosity andincrease the risk of forming a foamy slag. A foamy slag is undesirablebecause it creates process control issues.

The process may comprise controlling the process conditions so that theFeO content of the molten slag is at least 3 wt. % so that the moltenslag has a high oxygen potential.

The process may comprise controlling the process conditions so that theFeO content of the molten slag is at least 4 wt. % so that the moltenslag has a high oxygen potential.

The process may comprise controlling the process conditions so that theFeO content of the molten slag is at least 5 wt. % so that the moltenslag has a high oxygen potential.

The process may comprise controlling the process conditions so that theFeO content of the molten slag is less than 6 wt. %.

The process may comprise controlling the process conditions so that theFeO content of the molten slag is less than 10 wt. %.

The process may comprise controlling the process conditions so that thecarbon content of the molten slag is at least 3 wt. %.

The process may comprise controlling the process conditions so that thecarbon content of the molten slag is at least 4 wt. %.

The process may comprise controlling the process conditions so that thecarbon content of the molten slag is less than 5 wt. %.

The process may comprise controlling the process conditions so that theviscosity of the molten slag is in the range of 0.5-4 poise.

The process may comprise controlling the process conditions so that theviscosity of the molten slag is in the range of 0.5-3 poise.

The process may comprise controlling the process conditions so that theviscosity of the molten slag is greater than 2.5 poise.

The process may include adding one or more than one additive tofacilitate control of molten slag characteristics, for example slagcomposition and/or slag viscosity, in the molten bath.

By way of example, the additive may be selected to control basicity ofthe molten slag, for example by CaO addition, to decrease the viscosityof the slag and minimise the risk of a foamy slag.

The process may include controlling the process conditions so that themolten slag has the following constituents in the stated ranges:

-   TiO₂: at least 15 wt. %,-   SiO₂: at least 15 wt. %,-   CaO: at least 15 wt. %,-   Al₂O₃: at least 10 wt. %, and-   FeO: at least 3 wt. %.

The molten slag may comprise at least 20 wt. % TiO₂.

The molten slag may comprise at least 50 wt. % TiO₂.

The molten slag may comprise 15-20 wt. % SiO₂.

The molten slag may comprise 15-30 wt. % CaO.

The molten slag may comprise 10-20 wt. % Al₂O₃.

The molten slag may comprise 4-10 wt. % FeO.

The slag composition may include other constituents, such as MnO.

Specific examples of slag compositions in accordance with the presentinvention are as follows.

Chemistry A

SiO₂ 18.8 wt. % AL₂O₃ 15.2 wt. % CaO 15.3 wt. % MgO 10.9 wt. % MnO   0FeO  4.9 wt. % TiO₂ 33.1 wt. %

Chemistry B

SiO₂ 16.7 wt. % AL₂O₃ 13.0 wt. % CaO 25.1 wt. % MgO 10.2 wt. % MnO FeO 4.9 wt. % TiO₂ 28.8 wt. %

Chemistry C

SiO₂ 19.35 wt. % AL₂O₃ 16.46 wt. % CaO 16.17 wt. % MgO  12.1 wt. % MnO 2.16 wt. % FeO  6.0 wt. % TiO₂  25.7 wt. %

Chemistries A and B are based on the use of 100% feed material in theform of a Chinese titanomagnetite and chemistry C is based on the use of100% feed material in the form of a NZ titanomagnetite.

The process may include operating the process above atmospheric pressurein the direct smelting vessel.

The oxygen-containing gas may be oxygen-enriched air or technical gradeoxygen.

The process may comprise supplying solid feed materials into the vesselby injecting metalliferous feed material and solid carbonaceous materialand a carrier gas into the molten bath via solid material injectionlances that extend downwardly and inwardly through a side wall of thevessel so that the solid feed materials at least partially penetrate amolten iron layer of the molten bath.

The process may comprise controlling the process, including controllingthe injection of the solid feed materials and the carrier gas, toproduce substantial agitation of the molten bath.

The extent of the agitation of the molten bath may be such that there isa substantially uniform temperature in the bath.

The process may comprise discharging the molten metal and the moltenslag outputs of the process as separate process streams.

The process may comprise controlling the cooling rate of the molten slagdischarged from the process to preferentially form microstructures thatare amenable to processing in the sulphate process.

The process may be the HIsmelt process as described above.

The process may be a variant of the HIsmelt process involving a HIsmeltvessel in conjunction with either (a) a smelt cyclone on a directsmelting vessel, such as described in U.S. Pat. No. 6,440,195 and (b)pre-reduction of the metalliferous feed material prior to supplying thefeed material to the direct smelting vessel.

The present invention also provides a direct smelting vessel when usedto smelt a metalliferous feed material that contains iron oxides and atleast 3 wt. % titanium oxides via a molten bath-based direct smeltingprocess, with the vessel containing a molten bath of metal and slag, andwith the molten slag having a temperature range of 1400-1550° C. and aviscosity in a range of 0.5-5 poise.

The present invention also provides a molten iron product which maycontain vanadium metal produced by the above-described direct smeltingprocess.

The present invention also provides a slag product that has highconcentrations of titanium oxides in the form of TiO₂, such as at least50%, produced by the above-described direct smelting process.

The present invention also provides a feed material for the sulphateprocess for producing pigment-grade titania produced by theabove-described direct smelting process.

The present invention is described in more detail hereinafter withreference to the accompanying drawings, of which:

FIG. 1 is a diagrammatic view of a direct smelting vessel operating inaccordance with one embodiment of a direct smelting process of thepresent invention;

FIG. 2 is a tertiary phase diagram for calcia, alumina, and silica inslag in one embodiment of the direct smelting process of the presentinvention; and

FIG. 3 is a pseudo-tertiary phase diagram for a slag and separate slagliquidus plots for two marked sections of the phase diagram for a hightitanium oxide feed material in one embodiment of the direct smeltingprocess of the present invention.

The following description is in the context of smelting titanomagnetiteto produce molten iron via the

HIsmelt process. The present invention is not limited to smeltingtitanomagnetite and extends to smelting any suitable metalliferous feedmaterial that contains iron oxides and titanium oxides. For example, thepresent invention extends to smelting titanium-vanadium magnetite. Inaddition, the present invention is not limited to the HIsmelt processand extends to any molten bath-based process of the HIsmelt type ofprocess that can generate the necessary process conditions. Inparticular, by way of example, the present invention extends to variantsof the HIsmelt Process that include (a) a smelt cyclone on a directsmelting vessel, such as described in U.S. Pat. No. 6,440,195 and (b)pre-reduction of the metalliferous feed material prior to supplying thefeed material to the direct smelting vessel.

As is indicated above, the HIsmelt process is described in aconsiderable number of patents and patent applications in the name ofthe applicant. By way of example, the HIsmelt process is described inInternational application PCT/AU96/00197 in the name of the applicant.The disclosure in the patent specification lodged with the Internationalapplication is incorporated herein by cross-reference.

The process is based on the use of a direct smelting vessel 3.

The vessel 3 is of the type described in detail in Internationalapplications PCT/AU2004/000472 and PCT/AU2004/000473 in the name of theapplicant. The disclosure in the patent specifications lodged with theseapplications is incorporated herein by cross-reference.

The vessel 3 has a hearth 51 that includes a base and sides formed fromrefractory bricks, a side wall 53 which form a generally cylindricalbarrel extending upwardly from the sides of the hearth and include anupper barrel section and a lower barrel section, a roof 55, an off-gasduct 9 in an upper section of the vessel 3, a forehearth 67 fordischarging molten metal continuously from the vessel 3, and a tap hole(not shown) for discharging molten slag periodically from the vessel 3.

In use, the vessel contains a molten bath of iron and slag whichincludes a layer 15 of molten metal and a layer 16 of molten slag on themetal layer 15. The arrow marked by the numeral 17 indicates theposition of the nominal quiescent surface of the metal layer 15 and thearrow marked by the numeral 19 indicates the position of nominalquiescent surface of the slag layer 16. The term “quiescent surface” isunderstood to mean the surface when there is no injection of gas andsolid materials into the vessel. Typically, the temperature of themolten bath is in a range of 1400-1550° C.

The vessel 3 is fitted with a downwardly extending water-cooled hot airblast (“HAB”) lance 7 extending into a top space of the vessel 3 and aplurality of water-cooled solids injection lances 5 extending downwardlyand inwardly through a side wall and into the slag. The lances 5 extenddownwardly and inwardly at an angle of 30-60° to the vertical throughthe side wall and into the slag layer 16 in the molten bath. Theposition of the lances 5 is selected so that the lower ends are abovethe quiescent surface 17 of the metal layer 15 of the molten bath.

In use, titanomagnetite and coal and slag additives entrained in acarrier gas (typically N₂) are directly injected into the bath via thesolids injection lances 5.

The momentum of the injected solid materials/carrier gas causes thesolid material and gas to penetrate the metal layer 15. The coal isdevolatilised and thereby produces substantial volumes of gas in themetal layer 15. Carbon partially dissolves into the metal and partiallyremains as solid carbon. The iron oxides in the titanomagnetite aresmelted to molten metal and the smelting reaction generates carbonmonoxide gas. The gases transported into the metal layer 15 andgenerated via devolatilisation and smelting produce significant buoyancyuplift of molten metal, solid carbon, unreacted solid material in thetitanomagnetite (predominantly TiO₂), and slag (drawn into the metallayer 15 as a consequence of solid/gas/injection) from the metal layer15 which generates an upward movement of splashes, droplets and streamsof molten metal and slag and entrained unreacted titanomagetite, andthese splashes, and droplets, and streams entrain slag as they movethrough the slag layer 16.

The buoyancy uplift of the above-described material causes substantialagitation in the metal layer 15 and the slag layer 16, with the resultthat the slag layer 16 expands in volume and has a surface indicated bythe arrow 30. The extent of agitation is such that there is reasonablyuniform temperature in the metal and the slag regions—typically,1400-1550° C. with a temperature variation of the order of 30° in eachregion.

In addition, the upward movement of the above-described material extendsinto a top space 31 of the vessel 3 that is above the molten bath in thevessel and:

-   -   (a) forms a transition zone 23; and    -   (b) projects some molten material (predominantly slag) beyond        the transition zone and onto the section of the side wall of the        vessel 3 that is above the transition zone 23.

In general terms, the slag layer 16 is a liquid continuous volume, withsolid material and gas bubbles, and the transition zone 23 is a gascontinuous volume with splashes, droplets, and streams of molten metaland slag. Alternatively, the slag layer 16 may be described as a slurryof solid material in a liquid phase with a dispersion of gas bubbles inthe liquid phase.

The position of the oxygen-containing gas lance 7 and the gas flow ratethrough the lance 7 are selected so that the oxygen-containing gaspenetrates the central region of the transition zone 23 and maintains anessentially metal/slag free space (not shown) around the end of thelance 7. The lance 7 includes an assembly which causes theoxygen-containing gas to be injected in a swirling motion into thevessel.

The injection of the oxygen-containing gas via the lance 7 post-combustsreaction gases CO and H₂ in the transition zone 23 and in the free spacearound the end of the lance 7 and generates high temperatures of theorder of 2000° C. or higher in the gas space. The heat is transferred tothe ascending and descending splashes droplets, and streams, of materialfrom the metal layer and the heat is then partially transferred to themetal layer 15 when the material falls downwardly to the metal layer 15.

The described embodiment of the process of the present inventioncomprises controlling the process conditions so that the molten slag (a)is within a selected composition range so that the slag is a moltenslag, as described herein, (b) has a high oxygen potential, and (c) hasa viscosity in a range of 1-5 poise when the slag temperature is in arange of 1400-1550° C. in the molten bath in the vessel 3.

The necessary control of process conditions can be achieved by one ormore than one of a range of options, including but not limited tocontrolling the FeO content of the molten slag to achieve the requiredhigh oxygen potential and controlling the CaO content of the molten slagto achieve the required viscosity in the range of 1-5 poise when theslag temperature is in the range of 1400-1550° C. in the molten bath inthe vessel 3.

More particularly, in the described embodiment the necessary control ofprocess conditions includes selecting the feed materials and operatingconditions so that the molten slag has the following constituents in thestated range of 1400-1550° C. of the molten bath:

-   TiO₂: at least 15 wt. %,-   SiO₂: at least 15 wt. %,-   CaO: at least 15 wt. %,-   Al₂O₃: at least 10 wt. %, and-   FeO: at least 3 wt. %.

More particularly, in the described embodiment the necessary control ofprocess conditions includes controlling the slag composition so that themolten slag is sub-liquidus, preferably slightly sub-liquidus, for thatslag composition in the stated range of 1400-1550° C. of the molten bathso that a solid oxide phase precipitates from the liquid slag in anamount of 5-25% by volume of the slag. The resultant molten slag is aslurry of a solid oxide phase in a liquid slag phase. The precipitatedsolid oxide phase contributes to controlling the viscosity of the moltenslag as required for the described embodiment of the process. Inaddition, the viscous molten slag, is well-suited to form a protectivecoating on the refractories of the vessel in contact with the slag.

FIG. 2 is a tertiary phase diagram for three main slag constituents ofcalcia, alumina, and silica in one embodiment of the direct smeltingprocess of the present invention. More particularly, the phase diagramfocuses on two main gangue constituents of alumina and silica and a fluxadditive, namely calcia. The phase diagram was sourced from FactSage6.1. The phase diagram illustrates the impact of the slag composition onthe phases in the slag. In particular, it can be determined from FIG. 2that if a higher viscosity slag (i.e. a slag having a viscosity of atleast 2.5 poise) is required, this can be achieved by controlling theslag composition, for example by adjusting the calcia addition, andother process conditions to precipitate melilite solid phase from themolten slag.

FIG. 3 is a pseudo-tertiary phase diagram for a slag and separate slagliquidus plots for two marked sections of the phase diagram for a hightitanium oxide feed material in one embodiment of the direct smeltingprocess of the present invention. The phase diagram focuses on (a) threemain gangue constituents, namely alumina, magnesia, and silica, (b) aflux additive, namely calcia, and (c) titania. The phase diagram wassourced from University of Queensland researchers. The phase diagramdefines an operating window for slag compositions that provide therequired slag viscosities of 1-5 poise for the process. The Figurehighlights two sections of the phase diagram and these sections show thesignificant change in liquidus temperatures across the selectedcompositions. It is particularly evident from these sections theconsiderable scope to precipitate out solid phases and thereby changethe viscosity of the slag within the temperature range of 1400-1550° C.of the molten bath.

In more general terms, the following process features, separately or incombination, are relevant control parameters of the process.

-   -   (a) Controlling the slag inventory, i.e. the depth of the slag        layer and/or the slag/metal ratio (typically the weight ratio of        metal:slag to be between 3:1 and 1:1), to balance the positive        effect of metal in the transition zone 23 on heat transfer with        the negative effect of metal in the transition zone 23 on post        combustion due to back reactions in the transition zone 23. If        the slag inventory is too low the exposure of metal to oxygen is        too high and there is reduced potential for post combustion. On        the other hand, if the slag inventory is too high the lance 7        will be buried in the transition zone 23 and there will be        reduced entrainment of gas into the free space 25 and reduced        potential for post combustion.    -   (b) Selecting the position of the lance 7 and controlling        injection rates of oxygen-containing gas and solids via the        lance 7 and the lances 5 to maintain the essentially metal/slag        free region around the end of the lance 7 and to form the        transition zone 23 around the lower section of the lance 7.    -   (c) Controlling heat loss from the vessel by splashing with slag        the sections of the side wall of the vessel 3 that are in        contact with the transition zone 23 or are above the transition        zone 23 by adjusting one or more of:        -   (i) the slag inventory; and        -   (ii) the injection flow rate through the lance 7 and the            lances 5.

Many modifications may be made to the embodiment of the presentinvention described above without departing from the spirit and scope ofthe invention.

1. A direct smelting process that comprises supplying (a) ametalliferous feed material that contains iron oxides and at least 3 wt.% titanium oxides (b) a solid carbonaceous feed material, and (c) anoxygen-containing gas into a direct smelting vessel containing a moltenbath of iron and slag and direct smelting the metalliferous feedmaterial in the vessel and producing process outputs of molten iron,molten slag containing titanium oxides, and an off-gas, and the processbeing characterised by controlling the process conditions, as describedherein, so that the molten slag has a viscosity in a range of 0.5-5poise when the slag temperature is in a range of 1400-1550° C. in themolten bath in the direct smelting vessel.
 2. The process defined inclaim 1 wherein the molten slag is a slurry of a solid material and aliquid phase and the solid material is a solid oxide phase at the slagtemperature in the process, whereby the slag is a slurry of a solidoxide phase in a liquid slag phase.
 3. The process defined in claim 2comprising controlling the process conditions by controlling the slagcomposition and the temperature of the molten bath to be below theliquidus temperature of the slag so that the solid oxide phaseprecipitates from the liquid phase, thereby controlling the viscosity ofthe slag.
 4. The process defined in claim 2 comprising controlling theprocess conditions so that the solid material in the molten slag is atleast 5% of the molten slag.
 5. The process defined in claim 4comprising controlling the process conditions so that the solid materialin the molten slag is at least 10% of the molten slag.
 6. The processdefined in claim 5 comprising controlling the process conditions so thatsolid material in the molten slag is less than 30% of the molten slag.7. The process defined in claim 6 comprising controlling the processconditions so that solid material in the molten slag is 15-25% of themolten slag.
 8. The process defined in claim 1 wherein the metalliferousfeed material comprises any one or more than one of titanium magnetite,titanomagnetite and ilmenite.
 9. The process defined in claim 8 wherein,when the metalliferous feed material comprises titanomagetite only, thetitanium oxides are less than 40 wt. % of the metalliferous feedmaterial.
 10. The process defined in claim 8 or claim 9 wherein, whenthe metalliferous feed material comprises titanomagetite only, thetitanium oxides are less than 30 wt. % of the metalliferous feedmaterial.
 11. The process defined in claim 8 wherein, when themetalliferous feed material comprises titanomagetite and ilmenite, thetitanium oxides are less than 50 wt. % of the metalliferous feedmaterial.
 12. The process defined in claim 1 wherein the metalliferousfeed material also comprises other metal oxides such as vanadium oxides.13. The process defined in claim 12 wherein, where the metalliferousmaterial contains vanadium oxides, the process comprises producingprocess outputs of molten iron and vanadium, molten slag containingtitanium oxides and vanadium oxides, and an off-gas.
 14. The processdefined in claim 1 comprising controlling the process conditions bycontrolling the ratio of the concentrations of iron in the slag tocarbon in the metal to be less than 2:1.
 15. The process defined inclaim 1 comprising controlling the process conditions by controlling theratio of the concentrations of iron in the slag to carbon in the metalto be less than 1.5:1.
 16. The process defined in claim 1 comprisingcontrolling the process conditions by controlling the ratio of theconcentrations of iron in the slag to carbon in the metal to be 1:1 to1.3:1.
 17. The process defined in claim 1 comprising controlling theprocess conditions so that the molten slag has a high oxygen potential.18. A direct smelting vessel when used to smelt a metalliferous feedmaterial that contains iron oxides and at least 3 wt. % titanium oxidesvia a molten bath-based direct smelting process, with the vesselcontaining a molten bath of metal and slag, and with the molten slaghaving a temperature range of 1400-1550° C. and a viscosity in a rangeof 0.5-5 poise.
 19. A molten iron product produced by the directsmelting process defined in claim
 1. 20. A slag product that has atleast 50% titanium oxides in the form of TiO₂ produced by the directsmelting process defined in claim
 1. 21. A feed material for thesulphate process for producing pigment-grade titania produced by thedirect smelting process defined in claim 1.